Implement dynamic shadow call stack support on Clang, by parsing the
unwind tables at init time to locate all occurrences of PACIASP/AUTIASP
instructions, and replacing them with the shadow call stack push and pop
instructions, respectively.

This is useful because the overhead of the shadow call stack is
difficult to justify on hardware that implements pointer authentication
(PAC), and given that the PAC instructions are executed as NOPs on
hardware that doesn't, we can just replace them without breaking
anything. As PACIASP/AUTIASP are guaranteed to be paired with respect to
manipulations of the return address, replacing them 1:1 with shadow call
stack pushes and pops is guaranteed to result in the desired behavior.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20221027155908.1940624-4-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

For clarity and ease of maintenance, it would be helpful for all the
stack helpers to be in the same place.

Move the SDEI stack helpers into the stacktrace code where all the other
stack helpers live.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Kalesh Singh <kaleshsingh@google.com>
Reviewed-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Cc: Fuad Tabba <tabba@google.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220901130646.1316937-5-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Replace places that contain logic like this:
	is_hyp_mode_available() && !is_kernel_in_hyp_mode()

With a dedicated boolean function  is_hyp_nvhe(). This will be needed
later in kexec in order to sooner switch back to EL2.

Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-2-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>

The never-ending entry.S refactoring continues, putting us in a much
better place wrt compiler instrumentation whilst moving more of the code
into C.

* for-next/entry:
  arm64: idle: don't instrument idle code with KCOV
  arm64: entry: don't instrument entry code with KCOV
  arm64: entry: make NMI entry/exit functions static
  arm64: entry: split SDEI entry
  arm64: entry: split bad stack entry
  arm64: entry: fold el1_inv() into el1h_64_sync_handler()
  arm64: entry: handle all vectors with C
  arm64: entry: template the entry asm functions
  arm64: entry: improve bad_mode()
  arm64: entry: move bad_mode() to entry-common.c
  arm64: entry: consolidate EL1 exception returns
  arm64: entry: organise entry vectors consistently
  arm64: entry: organise entry handlers consistently
  arm64: entry: convert IRQ+FIQ handlers to C
  arm64: entry: add a call_on_irq_stack helper
  arm64: entry: move NMI preempt logic to C
  arm64: entry: move arm64_preempt_schedule_irq to entry-common.c
  arm64: entry: convert SError handlers to C
  arm64: entry: unmask IRQ+FIQ after EL0 handling
  arm64: remove redundant local_daif_mask() in bad_mode()

We'd like to keep all the entry sequencing in entry-common.c, as this
will allow us to ensure this is consistent, and free from any unsound
instrumentation.

Currently __sdei_handler() performs the NMI entry/exit sequences in
sdei.c. Let's split the low-level entry sequence from the event
handling, moving the former to entry-common.c and keeping the latter in
sdei.c. The event handling function is renamed to do_sdei_event(),
matching the do_${FOO}() pattern used for other exception handlers.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210607094624.34689-18-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

unwind_frame() was previously implicitly checking that the frame
record is in bounds of the stack by enforcing that FP is both aligned
to 16 and in bounds of the stack. Once the FP alignment requirement
is relaxed to 8 this will not be sufficient because it does not
account for the case where FP points to 8 bytes before the end of the
stack.

Make the check explicit by changing the on_*stack functions to take a
size argument and adjusting the callers to pass the appropriate sizes.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Ib7a3eb3eea41b0687ffaba045ceb2012d077d8b4
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210526174927.2477847-1-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>

* arm64/for-next/fixes: (26 commits)
  arm64: mte: fix prctl(PR_GET_TAGGED_ADDR_CTRL) if TCF0=NONE
  arm64: mte: Fix typo in macro definition
  arm64: entry: fix EL1 debug transitions
  arm64: entry: fix NMI {user, kernel}->kernel transitions
  arm64: entry: fix non-NMI kernel<->kernel transitions
  arm64: ptrace: prepare for EL1 irq/rcu tracking
  arm64: entry: fix non-NMI user<->kernel transitions
  arm64: entry: move el1 irq/nmi logic to C
  arm64: entry: prepare ret_to_user for function call
  arm64: entry: move enter_from_user_mode to entry-common.c
  arm64: entry: mark entry code as noinstr
  arm64: mark idle code as noinstr
  arm64: syscall: exit userspace before unmasking exceptions
  arm64: pgtable: Ensure dirty bit is preserved across pte_wrprotect()
  arm64: pgtable: Fix pte_accessible()
  ACPI/IORT: Fix doc warnings in iort.c
  arm64/fpsimd: add <asm/insn.h> to <asm/kprobes.h> to fix fpsimd build
  arm64: cpu_errata: Apply Erratum 845719 to KRYO2XX Silver
  arm64: proton-pack: Add KRYO2XX silver CPUs to spectre-v2 safe-list
  arm64: kpti: Add KRYO2XX gold/silver CPU cores to kpti safelist
  ...

# Conflicts:
#	arch/arm64/include/asm/exception.h
#	arch/arm64/kernel/sdei.c

* arm64/for-next/scs:
  arm64: sdei: Push IS_ENABLED() checks down to callee functions
  arm64: scs: use vmapped IRQ and SDEI shadow stacks
  scs: switch to vmapped shadow stacks

Now that the uaccess primitives dont take addr_limit into account, we
have no need to manipulate this via set_fs() and get_fs(). Remove
support for these, along with some infrastructure this renders
redundant.

We no longer need to flip UAO to access kernel memory under KERNEL_DS,
and head.S unconditionally clears UAO for all kernel configurations via
an ERET in init_kernel_el. Thus, we don't need to dynamically flip UAO,
nor do we need to context-switch it. However, we still need to adjust
PAN during SDEI entry.

Masking of __user pointers no longer needs to use the dynamic value of
addr_limit, and can use a constant derived from the maximum possible
userspace task size. A new TASK_SIZE_MAX constant is introduced for
this, which is also used by core code. In configurations supporting
52-bit VAs, this may include a region of unusable VA space above a
48-bit TTBR0 limit, but never includes any portion of TTBR1.

Note that TASK_SIZE_MAX is an exclusive limit, while USER_DS and
KERNEL_DS were inclusive limits, and is converted to a mask by
subtracting one.

As the SDEI entry code repurposes the otherwise unnecessary
pt_regs::orig_addr_limit field to store the TTBR1 of the interrupted
context, for now we rename that to pt_regs::sdei_ttbr1. In future we can
consider factoring that out.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: James Morse <james.morse@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201202131558.39270-10-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

In preparation for removing addr_limit and set_fs() we must decouple the
SDEI PAN/UAO manipulation from the uaccess code, and explicitly
reinitialize these as required.

SDEI enters the kernel with a non-architectural exception, and prior to
the most recent revision of the specification (ARM DEN 0054B), PSTATE
bits (e.g. PAN, UAO) are not manipulated in the same way as for
architectural exceptions. Notably, older versions of the spec can be
read ambiguously as to whether PSTATE bits are inherited unchanged from
the interrupted context or whether they are generated from scratch, with
TF-A doing the latter.

We have three cases to consider:

1) The existing TF-A implementation of SDEI will clear PAN and clear UAO
   (along with other bits in PSTATE) when delivering an SDEI exception.

2) In theory, implementations of SDEI prior to revision B could inherit
   PAN and UAO (along with other bits in PSTATE) unchanged from the
   interrupted context. However, in practice such implementations do not
   exist.

3) Going forward, new implementations of SDEI must clear UAO, and
   depending on SCTLR_ELx.SPAN must either inherit or set PAN.

As we can ignore (2) we can assume that upon SDEI entry, UAO is always
clear, though PAN may be clear, inherited, or set per SCTLR_ELx.SPAN.
Therefore, we must explicitly initialize PAN, but do not need to do
anything for UAO.

Considering what we need to do:

* When set_fs() is removed, force_uaccess_begin() will have no HW
  side-effects. As this only clears UAO, which we can assume has already
  been cleared upon entry, this is not a problem. We do not need to add
  code to manipulate UAO explicitly.

* PAN may be cleared upon entry (in case 1 above), so where a kernel is
  built to use PAN and this is supported by all CPUs, the kernel must
  set PAN upon entry to ensure expected behaviour.

* PAN may be inherited from the interrupted context (in case 3 above),
  and so where a kernel is not built to use PAN or where PAN support is
  not uniform across CPUs, the kernel must clear PAN to ensure expected
  behaviour.

This patch reworks the SDEI code accordingly, explicitly setting PAN to
the expected state in all cases. To cater for the cases where the kernel
does not use PAN or this is not uniformly supported by hardware we add a
new cpu_has_pan() helper which can be used regardless of whether the
kernel is built to use PAN.

The existing system_uses_ttbr0_pan() is redefined in terms of
system_uses_hw_pan() both for clarity and as a minor optimization when
HW PAN is not selected.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201202131558.39270-3-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>